It is generally known to provide a metallic rod or plate member on a circular double cylinder knitting machine for temporarily retarding or detaining the swinging movement of the needle latch to improve the plating of yarns during the formation of stitch loops. For example, Holmes et al U.S. Pat. No. 2,425,243 discloses such an arrangement in which a latch detainer plate is mounted for pivotal movement into and out of operative positions. When the latch detainer plate is in the operative position, the inner end of the horizontally disposed latch detaining plate is positioned so that its lower surface is engaged by the latches of the needles in the lower cylinder as they are being drawn downwardly to stitch forming position and its upper surface is engaged by the latches of the needles in the upper cylinder as they are being raised to stitch loop forming position. The latch detainer plate is controlled so that it is moved into operative position when the plating yarn feed finger is activated and the latch detainer plate is moved to the inoperative position when the plating yarn feed finger is moved to the inactive position.
A similar type of latch retarding device is disclosed in the Peberdy U.S. Pat. No. 2,495,543. The latch retarding device of this patent includes a metallic rod with a horizontally disposed flattened free end which is supported for movement between active and inactive positions. When moved to the active position, the lower portion of the flattened free end of the latch detaining member is engaged by the closing latches of the needles of the lower cylinder which are being lowered to a stitch forming position while the upper surface of the flattened free end portion of the latch detaining member is engaged by the closing latches of the needles in the upper cylinder as they are being raised to a stitch forming position. The latches are free to move to their fully closed position after they pass off of the free end of the flattened free end portion of the latch retarding device. The retarding of the movement of the latch to the closed position is provided for the purpose of enhancing the plating of yarns fed to the needles in the formation of rib fabric.
During present day high speed knitting on circular knitting machines the needles become worn to the place that they must be replaced within about three to twelve weeks of operation of the knitting machine. In many cases the failure of the needles is caused by the free end of the latch engaging the hook of the needle when the latch swings to the closed position during the movement of the needle to a lowered stitch loop forming position. The tip or spoon end of the latch engages the hook of the needle with a high impact force as the previously formed stitch loop swings the latch to the closed position as the loop rides up the needle and is shed therefrom. Needle wear is pronounced when open end spun cotton yarns are knit because many of these yarns include various types of contaminents, such as particles of silica which act as an abrasive when metal to metal contact is made between the spoon or tip of the latch and the end of the needle hook. Wear of the needle also occurs when the latch swings to the fully open position as the needle is raised to clear the stitch loop below the latch. In some cases the impact forces of the latch against the needle causes metal fatigue and latch failure.
The latch retarding or detaining devices disclosed in the above-identified patents are not satisfactory for use in cushioning the impact of the latch against the hook in present day high speed circular knitting machines because these devices are formed of metal and are not sufficiently resilient to momentarily interrupt and cushion the swinging movement of the latches during the final portion of the swinging movement. Also, the metallic latch detaining or retarding devices disclosed in these patents may cause undesirable wear of the latches.